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    CVE-2026-84128

    Privilege escalation in the WebDriver BiDi component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

    Published:Sep 1, 2026
    Last Modified:Sep 3, 2026
    EPS:Sep 1, 2026
    EPSS Score:0.00248
    CVSS Score:8.8

    Affected Products

    Vendor
    Mozilla
    Product
    Firefox
    Vendor
    Mozilla
    Product
    Thunderbird

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-284 Improper Access Control

    Related CVEs

    CVE-2026-84144 (CVSS 7.5) — Internally found bugs present in Thunderbird 154 and Thunderbird ESR 153.1. Some of these bugs showed evidence…
    CVE-2026-84143 (CVSS 9.8) — Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of th…
    CVE-2026-84142 (CVSS 9.8) — Internally found bugs present in Thunderbird 154. Some of these bugs showed evidence of memory corruption or a…
    CVE-2026-84141 (CVSS 9.8) — Integer overflow in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 155, Firefox ESR…
    CVE-2026-84140 (CVSS 9.8) — Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ES…
    CVE-2026-84139 (CVSS 6.1) — Clickjacking issue in the DOM: Events component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.…
    CVE-2026-84138 (CVSS 6.5) — Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 155 and Thunderbird 155…
    CVE-2026-84137 (CVSS 4.3) — Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 153…
    CVE-2026-84136 (CVSS 6.1) — Other issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, …
    CVE-2026-84135 (CVSS 9.8) — Other issue in Firefox Focus for Android. This vulnerability was fixed in Firefox 155.…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High